The Clifton Road grammar school last month sent back a sample of last year?s English Literature papers after some star pupils appeared to under-perform.

Now the London exam board, responsible for other gaffes in recent weeks, has asked for all 40 papers back for remarking in case other mistakes were made.

Lawrence Sheriff head teacher Peter Kent said the school was happy with the questions set but that the marks did not reflect the quality of the answers given.

He said: ?They looked at the papers again and have admitted that some of the marks need to be improved.

?I think this has confirmed that we were right to question whether the marking was up to the standard expected.

?I think the board has acted reasonably and they are trying to do the best they can to sort it all out.?

The results should be known in a month. A spokesman for Edexcel said: ?It is unusual for there to be a grade change but where a school has asked for papers to be remarked we use a different examiner to make sure everything is up to scratch. We try to be incredibly thorough.?

Mr Kent said it was ?massively in the students? interests? to get good AS-level marks as it counted towards half their A-level mark.

Edexcel recently set an impossible maths question and lost the coursework of 20 students. It has been told to show it can improve in time for the summer?s exams.